This website uses cookies

This website uses cookies to give you the best user experience. You have disabled cookies which will render many features of the GSL website unusable. To change your cookie settings, select the option below and follow the instructions. These instructions are also obtainable from the privacy & cookies link at the bottom of any GSL page.

This website uses cookies to give you the best user experience. If you continue without changing your settings we'll assume you are happy to receive all GSL cookies. To change your cookie settings, select the option below and follow the instructions. These instructions are also obtainable from the privacy & cookies link at the bottom of any GSL page.

The Geological Society offers grades of membership for every stage of your career, from student to retirement. Find out about the benefits of membership, and how we can help you achieve and maintain Chartered status.

Information about the Geological Society’s internationally acclaimed books and journals for authors, editors, librarians and readers. Order publications, find out about the Lyell Collection and read guidelines for preparing a paper or submitting a book proposal.

Information and resources for teachers and students from
primary education onwards; for those making careers choices
after A-levels including undergraduate and further degrees
at university; and for those seeking professional
geosciences training or exploring lifelong learning
opportunities.

News and updates for members of the public and policy makers interested in how the geosciences
interact with society. Find updates about outreach activities, policy related meetings, consultation responses and statements.

Geoscientist is the Fellowship magazine of the Geological Society: with news about science, people, the Society, features, reviews, opinion, letters and forthcoming events. All this, and more, can be found sooner here, in our online version.

The Geological Society of London is the UK national society for geoscience, providing support to over 11,500 members in the UK and overseas. Founded in 1807, we are the oldest geological society in the world.

News in Brief - October 2008

Snows of yesteryear

Do ice meteorites exist? And how can we find them if they do? Joe McCall investigates…

If we accept the chemical condensation model of the Solar System1,2 ice meteorites should exist. But they would melt on impact, in any temperature zone except Antarctica, where they could be recovered3. But how could we distinguish them from terrestrial ice? Such ‘dirty ice balls’ could be detected by studying their radioactive isotope content or organic chemicals. Acoustic and electromagnetic techniques (using long wavelengths, 10-40Hz) are likely to be useful and one would need a refrigerated transport system.

Hegyi et al.4 suggest using a Husar rover, equipped with suitable instruments. Ammonia and methane, they suggest, may be the clue to detection. They would drill to 3cm and place a gas sensor in the hole. Conductivity would be measured. Any sample would be recovered using a robotic arm, and GPS would position the recovery site precisely. They envisage three rovers working in parallel to cover a large area.

Fodor3 envisages extending the search to the Moon, ‘using the perpendicular
suspended LIDAR technique on the well known optical package which works as laser optical localisators’. This is an entirely new proposition and covers untried
methods. Scientists in China recovered in 1995 what they believed to be chunks of meteoritic ice which ‘plummeted to Earth’ in Zhejiang Province (just south of Shanghai)5. An amateur geologist, Zhong Gongpei, was nearby when farmers saw three large chunks of ice crash into paddy fields of Yaodou village. A cloudy streak and a ‘whooing sound’ were reported, before they crashed down in three fields one kilometre apart. One fist-sized piece left a crater one metre in diameter. A frozen food company kept them from melting. Meteorite expert Wang Sichao of the Purple Mountain Observatory, Jiangsu Province, said that they were probably ice meteorites, but further analysis was needed to confirm this, including analysis for isotopes and cosmic dust. The ice was apparently white, transparent, of irregular shape with air bubbles (?) on the surface and within. It was light and did not show the familiar layered structure of hailstones.

Was this a tall story? No mention of the analytical results is available 13 years later, and one must assume that the results were negative. One alternative possibility is that the lumps fell off the wing of an aircraft. There is also the question of friction in atmospheric entry. Ice meteorites would be likely to melt much further in - or entirely - on atmospheric entry: perhaps only quite large ice bodies would survive to land, even in Antarctica.

It is apparent that interest in ice meteorites has been revived and there will be searches in Antarctica and on the Moon, in the near future backed up my ‘state of the art’ technology. Mars, however, is too dusty to be a suitable location for such research3.

Jacking up the yak

Joe McCall reports on the surprisingly late timing of the Tibetan Plateau's uplift

The Himalayan-Tibetan Plateau, the World’s largest highland, plays an important role in driving the Asian Monsoons and global climate. However, the timing of its uplift remains a matter of debate. Researchers Yang Wang et al.1 suggest a rethink is in order.

A late Pliocene fauna has lately been discovered in the Kunlung Pass Basin - an asymmetric pull-apart. Bones and teeth of ancient herbivores were recovered from the Lower Qiangtang Formation, in and around two layers of organic rich mudstone - the age of which has been derived from palaeomagnetic studies as 2.5-2.0Ma (i.e., the lower part of the Matuyama division, Late Pliocene). The herbivore fossils include hipparionine horse, bovids, rhinoceros and other unidentified mammalian herbivores.

The authors compare this fauna with modern herbivores living around the Kunlung Pass – wild Tibetan asses, yak and five small mammals. The δ13C values from tooth enamel show that the diets of the fossil herbivores were very different from those of the present population. The δ18O values for the same tooth enamel also showed a significant change in the local meteoric water The δ18O values of fossil fish teeth and bones as well as gastropod shells, clearly indicate that in Late Pliocene time the Kunlung Pass Basin was occupied by a freshwater lake. The climate was warmer and wetter, hospitable to animal and plant life – very different from the rock desert and cold steppe of today. The authors conclude that the basin has been uplifted by ~2700 (+ or – 1600) metres since ~2-3 Ma, after the Late Pliocene, and later than commonly supposed.

Mars giant impact

Joe McCall finds room for doubt

The possible discovery of a huge crater on Mars is reported by Jeffrey Andrews-Hanna and colleagues from MIT1. This revives an old suggestion that the Borealis Basin is an impact structure. At 8200km across this would be the largest impact structure in the Solar System. Hitherto, the multi-ringed Valhalla Structure on Jupiter’s satellite Callisto held the crown, at ~4000 km diameter. There is no certainty, of course, that Valhalla is impact-generated but this multi-ringed form (one can count at least 13) is unknown among terrestrial impact structures. Andrews-Hanna admit that they have not proved impact origin, but they believe that they have shifted the tide.

The researchers also believe that the basin formerly held an ocean before Mars lost so much of its atmosphere, and its water either sublimated away or froze beneath the surface. Certainly there was more water circulating, probably much of it in hydrothermal systems rather than long lasting rivers, lakes and oceans, earlier in Mars’s history; but the evidence for such an ocean does not appear weighty.

It is said that the impact (?~4 billion years ago) was not so big as to melt everything; though Margaret Marinova2 (California Institute of Technology) believes that it was big enough to blast off half the martian crust. So where did it go? We have some small Mars-derived meteorites, but they are small objects. However there is not the slightest evidence, in the thousands of asteroid-sourced meteorites that have been examined (something like 30,000 in all) that there are an asteroidal/lunar and asteroidal/Martian composites. This is a quite amazing absence: I have drawn attention to it before, but it seems that scientists just do not want to know about it. I remain sceptical about such enormous impact structures, and wonder why Marinova believes this postulated giant impact would not have caused large-scale melting: there is much melt-rock produced by shock in much smaller terrestrial impact structures.

Transantarctic Mountains Again

I recently reported on the finds of Australasian strewn field microtektites trapped in local detritus and weathering pits, joints and fractures in the Transantarctic Mountains (Geoscientist 18.9 pp4). Alongside them a great number of micrometeorites have now also been recovered (tektites are micro-ejecta from large terrestrial impact structures; micrometeorites are microscopic extra-terrestrial particles).

Van Ginneken et al.1 describe six out of hundreds of 400-1100 μm-sized micrometorites recovered from the summits of Frontier Mountain and Miller Butte. There are literally thousands of smaller micrometorites with them, as well as cosmic spherules. The six specimens examined are of chondritic structure and mineralogy (olivine-pyroxene) and can be classified with the common H4 and L6 classes of common chondrite stony meteorites. When fresh they have a scoriaceous magnetite crust; but most are weathered, and covered with iron oxides and sulphate encrustations. Various degrees of weathering reflect different terrestrial residence ages; the fresher ones have a fusion crust, formed by surface melting on passage through the Earth’s atmosphere, just like megascopic meteorites.

This discovery, which is related to peculiar climatic conditions on this icy continent, opens up a whole field of research on the flux of nanoparticles to Earth.

Reference

And finally… Victorian greenhouse

The State of Victoria, with approximately five million inhabitants, four million of whom live in metropolitan Melbourne, relies for industrial and domestic energy on the brown coal (lignite) deposits of the Latrobe Valley, 150km east of Melbourne - making Victoria one of the highest per capita emitters of carbon dioxide in the world1.

Australia is committed to significant reductions on greenhouse gas production by 2050. Obviously, replacing the brown-coal fired energy generation must be considered. In the short term, replacing the coal-fired energy generation by natural gas, from the Bass Strait, irrespective of the benefits of waste reduction and use of renewable resources, is an option. Nuclear energy generation might be a long term solution, with no CO2 footprint; but although Australia has enormous uranium ore reserves, it has no downstream processing facilities, and only a single pilot scale nuclear plant, restricted to producing medical isotopes.

Any action will be taken to replace the Latrobe brown coal will depend on political factors, as any change is likely to be hugely unpopular in many quarters.